In the 3GPP (the 3rd Generation Partnership Project) which is the standardization group for a mobile communication system, the specification work of EPS (Evolved Packet System) described in Non Patent Literature 1 as the next generation mobile communication system has proceeded, a wireless LAN (WLAN) as well as LTE (Long Term Evolution) as an access system connected to the EPS has been examined.
In the 3GPP, as described in Non Patent Literature 2, proximity services (ProSe) that notify user equipment (UE) of the presence of other user equipment in proximity have been examined. In the ProSe, the UE can directly transmit and receive data to and from the proximity UE without a base station.
In the ProSe, since the data is directly transmitted and received between the UEs, a mobile communication network or a wireless LAN network is not used, and data traffic can be offloaded. Thus, it is possible to avoid the concentration of traffic in the LTE.
In the ProSe, the use of two methods as a direct communication path between the UEs has been examined. The first method is a method (hereinafter, referred to as LTE Direct) of establishing the direct communication path between the UEs using an LTE access technology, and the second method is a method of establishing the direct communication path using a wireless LAN access technology.
In the LTE Direct, the UE uses a commercial frequency allocated in an LTE system of each mobile communication provider, and directly transmits and receives data to and from the another UE by using an LTE communication system.
In the WLAN Direct, the UE uses a non-commercial frequency allocated in the WLAN, and directly transmits and receives data to and from the another UE.
In the ProSe, the necessity for the UE to detect the presence of the communication target UE in proximity by discovering a communication target UE in order to transmit and receive data through the LTE Direct or the WLAN Direct is given as a service required condition.
In order to provide a service by the mobile communication provider, direct communication between the UEs is defined as being required for an approval of the mobile communication provider at the time of establishing the direct communication path between the UEs.
As stated above, an object of the ProSe is to provide a service that notifies a certain UE of the presence of the proximity UE, and a service that provides communication through the direct communication path between the UEs.